Omron CQM1-TC102 Temperature Control Unit

The Omron CQM1-TC102 is a dedicated temperature control module for the CQM1 series compact PLC. This unit provides two independent closed-loop PID (Proportional-Integral-Derivative) control channels, each capable of reading a thermocouple temperature sensor and driving an output to maintain a precise setpoint. The CQM1-TC102 is designed for applications such as plastic injection molding barrel heating, drying ovens, heat sealing equipment, packaging machinery, and small industrial furnaces. By offloading temperature control from the main CPU, the module ensures accurate and responsive regulation while simplifying PLC programming.

Input and Sensor Compatibility

The CQM1-TC102 accepts thermocouple inputs on both channels. The supported thermocouple types include K, J, L, and optionally other types depending on the ordering code. The module provides cold junction compensation and linearization for the selected thermocouple type, delivering a temperature reading in degrees Celsius or Fahrenheit with a resolution of 0.1 degree. The input signal is isolated from the PLC’s internal logic to reduce noise interference. The thermocouple connections are made via a removable screw terminal block, accommodating both single and grounded tip thermocouples. The module also includes built-in burnout detection: if a thermocouple wire breaks or becomes disconnected, the module can detect the open circuit and trigger an alarm, preventing runaway heating. The input update rate is typically 500 milliseconds per channel, suitable for most thermal processes.

Control Outputs

Each of the two control loops has a dedicated output. The TC102 model features transistor outputs (open collector NPN) that can drive solid state relays (SSR) or interposing relays for contactor control. The outputs are typically configured for time-proportional control: the ON time is varied by the PID algorithm to modulate the heating power. The output cycle time is programmable, typically from 1 to 99 seconds. The transistor outputs are capable of switching up to 100 mA at 24 V DC, sufficient to drive the input of a typical SSR. For higher currents, a separate relay or contactor must be used. The module also supports alarm outputs: each channel can have up to two alarms (e.g., high temperature deviation, absolute high limit) that activate internal status bits or auxiliary outputs.

PID and Autotuning Functions

The CQM1-TC102 executes its own PID calculations independently of the main CPU, freeing the PLC processor for other tasks. The module stores PID parameters (proportional band, integral time, derivative time) for each channel in non-volatile memory. Users can adjust these values via the PLC’s data memory area. For simpler setup, the unit includes an autotuning (AT) function. When activated, the module performs a limit cycle tuning: it turns the output on and off to induce oscillations, measures the process response, and calculates optimal PID constants. The autotuning process can be initiated by setting a control bit from the program. The module also supports heating/cooling dual-loop control for applications that require both heating and active cooling, such as extrusion lines. In such mode, a second output (or a second channel) can be configured.

Integration with CQM1 CPU

The CQM1-TC102 occupies one slot in the CQM1 expansion rack and is addressed as a Special I/O Unit. The CPU communicates with the module via dedicated memory words: typically, each channel uses a set of registers for setpoint (SV), process value (PV), output value, and status. The user’s ladder program reads the PV to display on an HMI and writes the SV as commanded by the operator. The module can also be configured to operate in a simple ON/OFF mode (hysteresis control) if PID is not required. The unit includes LED indicators on the front panel showing power, loop status, and alarm conditions. The CQM1-TC102 is powered from the CQM1 backplane and does not require an external power supply for the control circuitry, though the output transistor supply must be provided externally.

Application Examples

In a plastic injection molding machine, the CQM1-TC102 can control the temperature of the barrel zones (nozzle, front, middle, rear) by regulating heaters based on thermocouple feedback. The autotuning feature compensates for changes in screw speed or ambient temperature. In a heat shrink tunnel, the module maintains a steady air temperature to ensure consistent packaging quality. For a food processing oven, the unit can log peak temperatures and trigger alarms if deviations exceed safe limits. The module’s ability to function independently of the main scan cycle makes it suitable for time-critical thermal processes.